Drawing ASTs for expressions: Correct Solution

For each of the Java expressions below:

• Draw an AST for the expression.
• Show how the expression evaluates at each node in the tree.

Be sure that your tree accurately reflects how Java would evaluate the expression.

Part 1

Given the following variables:

int seprang = 9;
double drecshia = 3.0;
double cecchrit = 2.0;
int kle = 1;

...draw the AST and evaluation results for the following expression:

seprang / (drecshia - 5) * cecchrit * kle

Solution

Things to double-check in your solution:

• Do you have the left and right branches on the correct side?
• Did you indicate the difference between ints and floating point values?

Part 2

Given the following variables:

double ubing = 4.0;

...draw the AST and evaluation results for the following expression:

2 <= ubing && 2 < 0 || (4 >= 9 && 2 > 0)

Solution

Things to double-check in your solution:

• Does your tree correctly reflect the precedence of && and ||?
• Did you correctly show short-circuiting? (That is when the right branch of && or || is never evaluated because the left branch already determines the answer.)

Part 3

Draw the AST and evaluation results for the following expression:

0 + 1 + 2 + 3 + 4 + "5"

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

Related puzzles:

• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9f-hLnp-95xa-qqn4-i)
• While loops and for loops: Correct Solution (1eeg-dtbh-w739-m3e)